Scanning electron microscope, an interface and a method for observing an object within a non-vacuum environment

ABSTRACT

An interface, a scanning electron microscope and a method for observing an object that is positioned in a non-vacuum environment. The method includes: generating an electron beam in the vacuum environment; scanning a region of the object with the electron beam while the object is located below an object holder; wherein the scanning comprises allowing the electron beam to pass through an aperture of an aperture array, pass through an ultra thin membrane that seals the aperture, and pass through the object holder; wherein the ultra thin membrane withstands a pressure difference between the vacuum environment and the non-vacuum environment; and detecting particles generated in response to an interaction between the electron beam and the object.

RELATED APPLICATIONS

This application claims priority of U.S. provisional patent Ser. No.61/077,955, filing date 3 Jul. 2008, U.S. provisional patent Ser. No.61/077,981, filing date 3 Jul. 2008, U.S. provisional patent Ser. No.61/077,977, filing date 3 Jul. 2008 and U.S. provisional patent Ser. No.61/077,970, filing date 3 Jul. 2008, which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

High resolution microscopy is used in research and development, qualityassurance and production in diverse fields such as material science,life science, the semiconductor industry and the food industry.

Optical microscopy, dating back to the seventeenth century, has reacheda brick wall defined by the wavelength of deep Ultra Violet photons,giving a finest resolution of about 80 nm. The popularity of opticalmicroscopy stems from its relative low price, ease of use and thevariety of imaging environmental parameters—all translated toavailability.

Scanning electron microscopy provides a much finer resolution (down to afew nanometers), but in order to achieve this high resolution theinspected object must be placed in a vacuum environment.

Determining a Working Distance

In non-vacuum Scanning Electron Microscopes, the distance between theobject and the microscope (also referred to as “working distance”) is ofthe order of a few to tens microns. Knowing the exact working distanceis important for resolution and contrast optimization, for safe imagingof an object without contacting the optics of the microscope, forreducing contamination generated by such a contact, and for generating afocused image by setting the focusing lens accordingly. There is agrowing need to provide a fast and accurate method and system fordetermining the working distance.

Reducing the Working Distance

The working distance between the object and the optics of the microscopeshould be as small as possible but large enough to prevent the objectfrom contacting the microscope or otherwise contaminating themicroscope. There is a growing need to provide an optimal trade offbetween the working distance and contamination hazards.

SUMMARY OF THE INVENTION

According to an embodiment of the invention a method is provided. Themethod is for observing an object that is positioned in a non-vacuumenvironment, the method includes: generating an electron beam in thevacuum environment; scanning a region of the object with the electronbeam while the object is located below an object holder; wherein thescanning comprises allowing the electron beam to pass through anaperture of an aperture array, pass through an ultra thin membrane thatseals the aperture, and pass through the object holder; wherein theultra thin membrane withstands a pressure difference between the vacuumenvironment and the non-vacuum environment; and detecting particlesgenerated in response to an interaction between the electron beam andthe object.

According to an embodiment of the invention a scanning electronmicroscope is provided. The scanning electron microscope includes: anelectron beam source positioned in a vacuum environment; the electronbeam source is adapted to generate an electron beam; an interfacebetween the vacuum environment and a non-vacuum environment in which anobject is positioned, the interface comprises an aperture array sealedby an ultra thin membrane that is substantially transparent to theelectron beam and withstands a pressure difference between the vacuumenvironment and the non-vacuum environment; an object holder; a scannerthat scans a region of the object with the electron beam while theobject is located below the object holder; wherein the electron beampasses through an aperture of the aperture array, passes through theultra thin membrane, and passes through the object holder; and adetector that detects particles generated in response to an interactionbetween the electron beam and the object.

According to an embodiment of the invention a method is provided. Themethod is for observing an object that is positioned in a non-vacuumenvironment, the method includes: illuminating an area of an object withan electron beam; wherein the electron beam is generated in the vacuumenvironment and passes through an aperture of an aperture array andpasses through an ultra thin membrane that seals the aperture; whereinthe ultra thin membrane withstands a pressure difference between thevacuum environment and the non-vacuum environment; detecting particlesgenerated in response to an interaction between the electron beam andthe object; and determining a distance between the object and the ultrathin membrane in response to detected particles.

According to an embodiment of the invention a scanning electronmicroscope is provided. The scanning electron microscope includes: anelectron beam source positioned in a vacuum environment; the electronbeam source is adapted to generate an electron beam; optics configuredto direct the electron beam towards an area of the object; an interfacebetween the vacuum environment and a non-vacuum environment in which anobject is positioned, the interface comprises an aperture array sealedby an ultra thin membrane that is substantially transparent to theelectron beam and withstands a pressure difference between the vacuumenvironment and the non-vacuum environment; at least one detector thatdetects particles generated in response to an interaction between theelectron beam and the object; and a controller configured to determine adistance between the object and the ultra thin membrane in response todetection signals generated by the at least one detector.

According to an embodiment of the invention a method is provided. Themethod is for aligning an electron beam and an aperture of an aperturearray, the method includes: obtaining an image of a first area of theaperture array; wherein the first area comprises multiple apertures ofthe aperture array; calculating a spatial relationship between aselected aperture of the multiple apertures and a reference locationwithin the first area; aligning an electron beam with the referencelocation in response to the spatial relationship; and obtaining an imageof a region of an object that is positioned in a non-vacuum environment;wherein the obtaining comprises scanning the region by an electron beamthat is generated in a vacuum environment, passes through the selectedaperture and passes through an ultra thin membrane that seals theselected aperture; wherein the ultra thin membrane withstands a pressuredifference between the vacuum environment and the non-vacuumenvironment.

According to an embodiment of the invention a scanning electronmicroscope is provided. The scanning electron microscope includes: anelectron beam source positioned in a vacuum environment; the electronbeam source is adapted to generate an electron beam; an interfacebetween the vacuum environment and a non-vacuum environment in which anobject is positioned, the interface comprises an aperture array sealedby an ultra thin membrane that is substantially transparent to theelectron beam and withstands a pressure difference between the vacuumenvironment and the non-vacuum environment; optics configured to scan,with an electron beam, a first area of the aperture array and scan asecond area of the aperture array; wherein the first area comprisesmultiple apertures of the aperture array; wherein the second area issmaller than the first area and comprises a selected aperture; at leastone detector that detects particles generated in response to aninteraction between the electron beam and at least one entity out of theinterface and the object; and a controller configured to: calculate aspatial relationship between a selected aperture of the multipleapertures and a reference location within the first area; and control analignment of the electron beam with the reference location in responseto the spatial relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a portion of a scanning electron microscope accordingto an embodiment of the invention;

FIG. 2 illustrates a portion of a scanning electron microscope accordingto another embodiment of the invention;

FIG. 3 illustrates an object, a sample holder, non-vacuum environmentand a chamber according to an embodiment of the invention.

FIG. 4 illustrates a chamber that includes a force applying componentaccording to an embodiment of the invention;

FIG. 5 is a cross section of an object that is an electrochemical celland of a sample holder according to an embodiment of the invention;

FIG. 6 illustrates a method for observing an object that is positionedin a non-vacuum environment, according to an embodiment of theinvention;

FIGS. 7 and 8 illustrate a first area of an aperture array according toembodiments of the invention;

FIG. 9 illustrates a method for aligning an electron beam and anaperture of an aperture array, according to an embodiment of theinvention;

FIG. 10 illustrates an object holder and multiple objects according toan embodiment of the invention;

FIG. 11 illustrates a portion of a scanning electron microscope andvarious particles according to an embodiment of the invention;

FIG. 12 illustrates a relationship between working distance and electrondistribution according to an embodiment of the invention;

FIG. 13 illustrates a ratio between the fraction of electrons that donot pass through an aperture array and the fraction of electrons thatpass through the aperture array, according to an embodiment of theinvention;

FIG. 14 illustrates a contrast, according to an embodiment of theinvention;

FIG. 15 illustrates a method for observing an object that is positionedin a non-vacuum environment, according to an embodiment of theinvention;

FIG. 16 illustrates an effect of placing a shutter on the collectionefficiency according to an embodiment of the invention;

FIG. 17 illustrates a relationship between working distances and acalculated shutter diameter for onset of signal saturation (equilibriumpoint) according to an embodiment of the invention;

FIG. 18 illustrates a detector that includes two concentric annulardetector elements (electrodes) according to an embodiment of theinvention;

FIG. 19 illustrates collection efficiencies for the detector of FIG. 18,as a function of working distance according to an embodiment of theinvention;

FIG. 20 illustrates an off axis illumination according to an embodimentof the invention;

FIG. 21 illustrates an annular BSE detector that has two segmentsaccording to an embodiment of the invention;

FIG. 22 illustrates an off-axis illumination according to an embodimentof the invention;

FIG. 23 illustrates a relationship between a difference signal andworking distance for off axis illumination according to an embodiment ofthe invention;

FIG. 24 illustrates on-axis and off-axis illumination according to anembodiment of the invention; and

FIG. 25 illustrates a scanning electron microscope and anothermicroscope according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

According to various embodiments of the invention a scanning electronmicroscope and a method are provided. An object is placed, in anon-vacuumed environment, underneath an object holder that may includeat least one partially transparent foil. The foil can be of the typescommonly used in transmission electron microscope (TEM) grid, with theobject placed onto the side far from the microscope. (It is so-called“inverted”). Alternatively, the object can be placed on top of foil thatis then flipped, turned or otherwise inverted.

The object holder may include at least one fully transparent portion, atleast one partially transparent portion or a combination thereof.

This configuration allows placing non-solid objects such as gels,liquids, biological cells to be placed such as to contact a lower sideof the sample holder and this sample holder can be positioned at smalldistance from the scanning electron microscope optics (from theinterface between a vacuum environment and a non-vacuum environment)thus minimizing the possibility of contact with the scanning electronmicroscope. This configuration also allows placing objects such aspowders, flakes, or particular small crystals.

This so called inverted configuration prevents contamination of thescanning electron microscope optics while providing a small workingdistance.

The inverted configuration also facilitates having the sample in aseparate environment (also referred to as mini-environment) andcontrolling a temperature of the mini environment, controlling apressure maintained in the mini environment, controlling a gascomposition of the mini environment, providing solvents to the minienvironment and applying mechanical stress levels on the object orwithin the mini environment. The inverted configuration also facilitatesthe addition of chemicals to the mini environment whether in gas, liquidor solid particles form.

The inverted configuration also allows connecting the sampleelectrically to testing equipment. The electrical connectors can beconnected to the lower part of the object holder or integrated within.

The inverted configuration also allows irradiating the sample withphotons by a light source that can be a part of another microscope orinspection tool.

All the manipulations mentioned above in relation to the minienvironment can be executed prior to imaging with the electronmicroscope or during imaging which allows to image changes in real time.

The sample holder can be connected to, or placed on, two or three axesstage (such as a XYZ stage) that can move the object holder and hencemove the object for various purposes such as but not limited toalignment with a selected aperture, moving the object to be inspected byanother inspection tool or microscope, and the like.

According to an embodiment of the invention the sample holder can bemoved (while maintained in a mini-environment) to an imaging ormeasurement probe or tool located on a different platform or differentsystem.

The object holder can be made of a very thin foil that has minimumimpact on the image resolution and contrast. The foil can be transparentboth for photons and electrons with typical energies of 5-30 kV.

The object holder is located in the non-vacuum environment and does notneed to withstand a pressure gradient between the vacuum environment andthe non-vacuum environment—thus simplifying its manufacturing processand expanding the range of materials that can be used.

The foil can also be reinforced with a grid structure which can beplaced on either the side facing the electron microscope, the sideopposite the electron microscope or on both sides.

The inverted sample holder can be made of multiple compartments enablingputting multiple samples on the same holder for analysis.

The inverted configuration facilitates a scanning of an object that isan electrochemical cell and generating images (in real time) ofelectrochemical processes for example deposition. One of the electrodesof the electromechanical cell can be shaped as a grid and can be used tosupport a foil of the object holder. This electrode can be imaged withthe scanning electron microscope. Another electrode of theelectrochemical cell may contact a solution positioned at a lower partof the electrochemical cell.

The inverted configuration also facilitates connecting the sample to anexternal electrical power source either having the entire object at adesired potential or connecting more than a single electrode forcreating potential differences on the foil.

According to an embodiment of the invention a method is provided. Themethod may include placing an object such as a non-solid object on alower side of an object holder such that the object contacts at leastone partially transparent portion (such as a foil) of the object holder;imaging the object, while placed on the lower side of the sample holderby at least one scanning electron microscope.

Scanning Electron Microscope

FIG. 1 illustrates a portion of scanning electron microscope 100according to an embodiment of the invention. FIG. 2 illustrates aportion of scanning electron microscope 100 according to anotherembodiment of the invention.

FIG. 1 illustrates an “inverted configuration” of scanning electronmicroscope 100 while FIG. 2 illustrates a non-inverted configuration ofscanning electron microscope 100. It is noted that a scanning electronmicroscope that can operate in both configurations as well as a scanningelectron microscope that can operate at only one of these configurationscan be provided without departing from the spirit of the invention.

The inverted configuration allows a reduction of the working distance byplacing the object below an object holder—placing the object at a sidethat does not face the interface between the vacuum and non-vacuumenvironments.

Scanning electron microscope 100 includes electron beam source 110,interface 120, object holder 130, optics 140, scanner 140 and one ormore detectors such as detectors 150 and 160. Scanner 140 is illustratedas including multiple deflection coils 140. It can also include amechanical stage that can move object holder 130 and therefore object10.

Electron beam source 110 is positioned in vacuum environment 170.Electron beam source 110 is adapted to generate electron beam 20.

Interface 120 is positioned between vacuum environment 170 andnon-vacuum environment 180. Object 10 is positioned in non-vacuumenvironment 170. Interface 120 includes aperture array 122 that issealed by an ultra thin membrane 124 that is substantially transparentto electron beam 20 and withstands a pressure difference between vacuumenvironment 170 and non-vacuum environment 180.

Object holder 130 holds object 10. FIG. 1 illustrates object holder 130as placed above object 10.

Scanner 140 scans a region of object 10 with electron beam 20 whileobject 10 is located below object holder 130. Object 10 is below objectholder 130 in a sense that it is not placed on an upper part of objectholder 130—it does not face the interface 120. Accordingly, electronbeam 20 has to pass through object holder 130 or a dedicated portionthereof in order to interact with object 10.

When scanner 140 scans the region of object 10 electron beam 20 passesthrough one or more apertures of aperture array 122, passes throughultra thin membrane 124, and passes through object holder 130. Objectholder 130 can include portions that are transparent or substantiallytransparent to electron beam 20. Object holder 130 can include a gridthat can contact object 10.

Object 10 may be a non-solid object such as fluid, gel, emulsion,biological cell and the like. Object 10 may also be one or more smallparticles, a powder and the like.

Object 10 may be placed above object holder 130 and object holder 130can be rotated or otherwise moved or manipulated so that when beingscanned by electron beam 20 it is below object holder 130.Alternatively, object 10 may be provided to the lower part of objectholder 130 without rotating or otherwise moving object holder 130.

According to an embodiment of the invention object 10 does not contactthe lower part of object holder 130 but contacts a gel or emulsion orother non-solid material that contacts object holder 130. Object holder130 can be shaped to contact a non-solid entity in which the object isinserted. It can include a rigid lower side in order to provide betterconnectivity to the non-solid entity.

One or more objects can be located below object holder at a time.Accordingly, object holder 130 can include multiple object holderregions, each region is shaped to contact an object 10. FIG. 10illustrates object holder 130 as holding multiple objects 11 in multipleregions 139.

Referring back to FIG. 1, each of detectors 150 and 160 detect particlesgenerated in response to an interaction between electron beam 20 andobject 10. Detector 150 is located in vacuum environment 170 whiledetector 160 is located in non-vacuum environment 180.

FIG. 1 illustrates detector 150 as having an aperture through whichelectron beam 20 passes. It is referred to as “in lens” detector. It caninclude different detector elements—each capable of generating its owndetection signals. Each detector element can also be referred to as adetector.

Detector 160 is positioned in non-vacuum environment 180. It can beconnected to interface 120 and measure a current that flows thoughinterface 120. Additionally or alternatively, detector 160 can detectelectrons that do not pass through aperture array 122 in other manners.

Scanning electron microscope 100 can be used for various purposes,including but not limited to: (i) image voltage contrast in air; (ii)electron beam lithography on photo resist in air; (iii) high resolutionimaging of wafers and processes which are incompatible with vacuum suchas a photo resist before curing; (iv) image and analyze wafers andprocesses which are impacted by the vacuum environment, or wafers andprocesses which are sensitive to formation of adhesion of a monolayer ofcontamination molecules; (v) image and analyze large specimen such assolar panels and flat panel display; (vi) image and analyze particles ina solution; (vii) image histology and pathology slides; (viii) imagebiological cell; (ix) excite X-ray emission for material analysis,whereas an image can be used to find a known location and generate ananalysis on an exact location; (x) excite X-ray emission for thicknessmeasurement, whereas an image can be used to find a known location andgenerate an analysis on an exact location; (xi) excite X-ray emissionfor density measurement, whereas an image can be used to find a knownlocation and generate an analysis on an exact location; (xii) image andanalyze side walls, whereas an image can be used to find a knownlocation and generate an analysis on an exact location, (xiii) image andmeasure thickness of side walls, whereas an image can be used to find aknown location and generate an analysis on an exact location, and thelike.

Aperture Array 122 and Ultra Thin Membrane 124

The term aperture array means any arrangement (ordered or non-ordered)of apertures. The apertures of the array can be sealed by one or moreultra thin membranes.

Conveniently, the ultra thin membrane is thinner than a 100 nanometersand is made of low density material such as Carbon or SiN.

When multiple apertures are provided each aperture can be sealed by itsown membrane, although this is not necessarily so. A single membrane canseal multiple apertures. According to an embodiment of the invention themembrane can be connected to a very thin grid that defines multipleapertures.

The ultra thin membrane seals an aperture while withstanding thepressure difference between the vacuum environment and the non-vacuumenvironment.

The ultra thin membrane is used because it has the minimal impact on theelectron spot size. For better performance it is advantageous to usehigher electron accelerating voltages, preferably 20 kV and higher.Another advantage of using ultra thin membrane is that the electronsused to generate the image can be efficiently collected with detectorssituated in the vacuum environment.

The aperture array can include an aperture array of different sizedapertures that are sealed by membranes of different areas and thickness.The different apertures can be positioned at the same plane, but this isnot necessarily so. For example, apertures and membranes can bepositioned in a staggered manner. The apertures positioned at the centerof the aperture array can be lower than aperture positioned near theedges of the aperture array. The apertures of the array can bepositioned in different planes that are arranged in a symmetrical mannerabout the center of the aperture array or in relation to a symmetryaxis, but this is not necessarily so.

Different apertures can be sealed by ultra thin membranes (or differentportions of the same ultra thin membrane) of the same thickness.Alternatively, different apertures can be sealed by ultra thin membranes(or different portions of the same ultra thin membrane) of differentthickness.

The thickness can be responsive to the size of the aperture. Largerapertures may be sealed by thicker membranes. Larger apertures providelarger field of view but thicker membranes reduce the resolution.Accordingly, a system that includes membranes of different thickness andapertures of different areas can provide multiple trade-offs betweenfield of views and resolution.

The different apertures can be accessed by moving the apertures to theelectron beam position, and/or by deflecting the electron beam.According to another embodiment of the invention an aperture arrayincludes evenly sized apertures and conveniently evenly sized membranes.

The apertures of the aperture array can all have the same shape but thisis not necessarily so. Non limiting examples of apertures shapes includecircles, ellipse, square, triangle, rectangle, and the like.

An entire area of the object can be imaged by scanning that area by anaperture array. The scanning axis can be parallel a longitudinal axis ora latitudinal axis of the aperture array but can also be oriented inrelation to these arrays.

It is noted that when virtually combining the field of view provided byeach of the apertures a relatively large (though not continuous) fieldof view can be obtained. A non-continuous image of sub-areas of theobject can be used during navigation stages.

An aperture array can be manufactured in various manners includingdeposition and etch back. The deposition includes depositing one or moreultra thin membrane on an aperture array. The etch back process includesetching a plate in order to form multiple apertures.

It is noted that different aperture arrays or different aperture can beused in an interchangeable manner. An interface of a scanning electronmicroscope can include multiple aperture arrays and at a given point oftime one (or more) aperture array can be illuminated by one or moreelectron beams.

Scanner 140

Scanner 140 can scan an area or a region of object 10 by at least one ofthe following or a combination of both: (i) electrostatic scanning ofelectron beam 20; (ii) mechanical scanning of the object with electronbeam 20 in spot mode to form an image, which can be useful if oneutilizes a very small aperture and wants to generate an image with fieldof view larger than the size of the aperture; (iii) mechanical scanningof the microscope with electron beam 20 in spot mode to form an imagewhich can be useful if one utilizes a very small aperture and wants togenerate an image with field of view larger than the size of theaperture; (iv) mechanical scanning of the aperture or windowsimultaneously with electrostatic scanning of electron beam 20 so thatelectron beam 20 follows the window position; (v) scanning the apertureby magnetic scanning.

FIG. 1 illustrates scanner 140 as placed between interface 120 andelectron beam source 110 but this is not necessarily so. Forexample—scanner 140 can include a stage (such as stage 240 of FIG. 2)that can move object 10. The stage can be connected to object holder 130or be a part of object holder 130.

Detectors 150, 160

Particles such as electrons that interact with the object can causevarious particles to be scattered or reflected from the object. Theinteraction can generate secondary electrons, backscattered electrons,characteristic X-rays and in some cases Cathodoluminescence. TheCathodoluminescence can be either a surface property or caused due tolight emission from markers or labeling molecules. The emitted signal isdetected with the aid of one of the mentioned above detectors.

FIG. 1 illustrates scanning electron microscope 100 as includingdetector 150 and detector 160. It is noted that scanning electronmicroscope 100 can include more or less detectors. For example—scanningelectron microscope can have more than a single detector within vacuumenvironment 170 and, additionally or alternatively, have more than asingle detector in non-vacuum environment 180.

According to embodiments of the invention, scanning electron microscope100 can have only vacuum environment detectors or have only non-vacuumenvironment detectors. A combination of both can also be provided thusone or more detector is positioned in the non-vacuum environment whileone or more other detectors are positioned in the vacuum environment.

Locating one or more detector such as vacuum environment detector 150 invacuum environment 170 can facilitate small and even very small workingdistances between the object and one or more apertures, thus contributeto the resolution of the image. Placing detectors in the vacuumenvironment also enables to use detectors that are less compatible withair such as using coatings which easily oxidize.

It is noted that using different detectors can provide more informationabout the illuminated area of the object and that multiple detectors canbe activated simultaneously.

Detectors 150 and 160 can detect the same type of particles. Accordingto another embodiment different detectors of scanning electronmicroscopes can detect different types of particles.

For example—one detector of scanning electron microscope 100 can detectbackscattered electrons (BSE). A BSE detector can be located betweenultra thin membrane 124 and an objective lens (not shown) of scanningelectron microscope 100. The BSE detector can have an annular shape thatdefines an opening enabling electron beam 20 to pass. The BSE detectorcan also be segmented to enhance topography information.

According to another embodiment one detector can detect electrons andanother detector detects light. Both detectors may operatesimultaneously.

A parabolic mirror (not shown) located between ultra thin membrane 124and an objective lens of scanning electron microscope 100, having anopening enabling electron beam 20 to pass will collect the light to aphotomultiplier placed to the side of the electron path.

Scanning electron microscope 100 can include one or more X-ray detectorsthat can assist in material analysis. Integrating such analysis to animaging engine permits localization of the object to be analyzedenabling higher sensitivity for smaller objects as opposed tomacroscopic analysis. Another possibility is to use emitted X-rays forimage generation which is commonly referred to as X-ray mapping.

For analysis with low resolution where working distance of >100 micronscan be applied, an X-ray detector can be located outside the vacuumenvironment. It would be preferable to use an annular detector toincrease the collection efficiency.

For analysis with high resolution, where smaller working distance has tobe applied, lets say <100 microns, the detector will be situated insidethe vacuum. If a side detector is used it can be in a configurationwhere backscattered electrons, secondary electrons and light can bedetected. An alternative arrangement where emphasis is on high X-raycollection efficiency is to use an annular X-ray detector such as amulti cell Silicon drift detector (SDD) manufactured by PN Sensor,Germany.

Vacuum Environment 170

A scanning electron microscope column can operate under vacuum. Thecolumn of scanning electron microscope 100 can include multipledifferentially pumped spaces that are separated by a non-sealedaperture. It is noted that the sealing provided by interface 120 canrender such a partition unnecessary. It is noted that the vacuum ofvacuum environment 170 can be provided by one or more pumps such as anion pump, a turbo pump and the like. Since the system is isolated amicroscope can be designed without a pump as done in a CRT.

Non-Vacuum Environment 180

The environment between the sample and the column can be of anycomposition. In particular, it can be filled with air, at leastpartially filled with nitrogen or dry nitrogen where the efficiency oflight emission due to secondary gas excitation is high because theoxygen which is a quencher of this process is absent. Non-vacuumenvironment 180 can be at least partially filled with inert gases and inparticular He or mixture of He where the mean free path of the electronis higher improving the signal to noise at larger working distances.

Inverted Configuration

FIG. 3 illustrates object 10, sample holder 130, non-vacuum environment180 and chamber 210 according to an embodiment of the invention.

Chamber (also referred to as micro-chamber) 210 can define a space inwhich mini environment 220 can exist. Mini environment 220 is definedaround object 10. Mini environment 220 is smaller than non-vacuumenvironment 180 and may be even much smaller. For example it can be 5%,10%, 20% or 30% of the non-vacuum environment, but this is notnecessarily so.

Chamber 210 can control one or more characteristics of mini environment220 by introducing one or more chemicals, by heating or cooling minienvironment 220, by drying of introducing vapors such as to determine ahumidity of mini environment 220, by directing radiation towards object10, by applying force (for example squeezing object 10 against objectholder 130), and the like.

Chamber 210 includes frame 218, inlet 212, outlet 214, temperatureaffecting element 216 (such as a cooling element, a heating element orboth). Inlet 212 can be used to inject one or more chemicals, gases,fluids and the like.

FIG. 3 illustrates sample holder 130 as including a transparent portion132 (such as a semi transparent film) and sample holder base 134. Object10 is positioned below transparent portion 132.

FIG. 4 illustrates chamber 210 that includes force applying component230 according to an embodiment of the invention. Force applyingcomponent 230 can apply force on object 10 while object 10 is withinmini environment 220. It is noted that scanning electron microscope 100can include a force applying component even without having chamber 210.

FIG. 5 is a cross section of an object 10 that is an electrochemicalcell 250 and of sample holder 130 according to an embodiment of theinvention.

Electromechanical cell 250 includes electrolyte solution 251 thatcontacts semi transparent film 136 of sample holder 130 that in turn issupported by conducting grid 138. Conducting grid 138 serves as one ofthe electrodes of electromechanical cell 250 and can be electricallycoupled (via connector 252) to an electrical device (not shown). Secondelectrode 253 of electrochemical cell 250 can contact electrolytesolution 251. Sample holder base 134 can be made of an insulatingmaterial.

FIG. 6 illustrates method 600 for observing an object that is positionedin a non-vacuum environment, according to an embodiment of theinvention.

Method 600 may start by initializing stage 610. Stage 610 can includeplacing the object below the object holder, affecting a parameter of amini environment in which the object is positioned and the like:

Stage 610 can include placing the object such as to contact a lower sideof the object holder, placing the object such as to contact a foil ofthe object holder, placing the object on the object holder and thanrotating or otherwise manipulating the object holder so that the objectis placed below the object holder.

Stage 610 can include placing the object within a non-solid entity thatcontacts a lower side of the object holder and scanning a region of theobject.

Stage 610 may include placing multiple objects below the object holder.

Stage 610 may include imaging the object by a low magnificationtechnique such as optical microscope to facilitate navigation to theobject. Alternatively, stage 610 can include navigating to the object inresponse to an image of the object (or object vicinity) that may beacquired by applying an imaging process that differs (at least by itsresolution) from the imaging process that is executed during stages630-650.

Stage 610 is followed by stage 620 of generating an electron beam in thevacuum environment. Stage 620 can include generating multiple electronbeams.

Stage 620 is followed by stage 630 of scanning a region of the objectwith the electron beam while the object is located below an objectholder. Stage 630 of scanning includes allowing the electron beam topass through an aperture of an aperture array, pass through an ultrathin membrane that seals the aperture, and pass through the objectholder. The ultra thin membrane withstands a pressure difference betweenthe vacuum environment and the non-vacuum environment.

Stage 630 can include scanning one or more regions of one or moreobjects by one or more electron beams.

Stage 630 may include at least one of the following or a combinationthereof: (i) scanning at least one region of the object by deflectingthe at least one electron beam and introducing a correspondingmechanical movement of the aperture array; (ii) scanning at least oneregion of the object by deflecting the at least one electron beam andintroducing a corresponding mechanical movement of the aperture array;wherein a component that includes the aperture array is flexiblyconnected to another component of an interface that separates the vacuumenvironment from the non-vacuum environment; (iii) scanning multipleregions of the object by deflecting 15—the at least one electron beamthat pass through multiple apertures of the aperture array; (iv)scanning multiple regions of the object by deflecting the at least oneelectron beam that pass through multiple apertures of the aperture arrayand introducing a corresponding mechanical movement of the aperturearray; (v) scanning a region of the object by deflecting the at leastone electron beam by a deflector positioned within the vacuumenvironment.

Stage 630 is followed by stage 640 of detecting particles generated inresponse to an interaction between the electron beam and the object.

Stage 640 is followed by stage 650 of processing detection signalsgenerated as response to the detection of particles. Stage 650 caninclude generating an image of the region of the object, determining astate of the object, or evaluating other parameters of the object. Theprocessing can be preceded by, followed by or executed in parallel ofstoring the detection signals.

According to an embodiment of the invention method 600 includes stage670 of imaging the object by another microscope while the object islocated below the object holder. The other microscope can be an opticaltool that directs light towards the lower part of the object. FIG. 25illustrates another microscope such as optical microscope 2400 thatimages object 10 while object is located below object holder 130.Optical microscope 2400 directs a light beam 2410 that propagates alongan optical axis that is normal to object 10—as illustrated by dashedline 2410. FIG. 25 illustrates optical microscope 2400 and scanningelectron microscope 100 as having optical axes that are opposite to eachother. It is noted that the optical axis of these microscopes can beoriented in relation to each other by angles that may differ from 180degrees. Both microscopes 100 and 2400 can image or scan objectsimultaneously, in a partially overlapping manner or in anon-overlapping manner in which each microscope images or scans object10 during non-overlapping periods.

Stage 610 can include placing the object within a chamber that defined amini environment that at least partially surrounds the object. Stage 600can include stage 680 of controlling at least one characteristic of themini environment during the scanning of the region of the object. Thecontrolling can include inducing at least one chemical within the minienvironment, applying force on the object while the object is scanned,changing a temperature of the mini environment, changing a humidity ofthe mini environment, and the like.

Alignment of Electron Beam 20

Referring back to FIG. 1, each of detectors 150 and 160 can senddetection signals that may be processed by controller 190 in order togenerate an image of the area of object 10.

An area of the object can be scanned by directing electron beam 20through a selected aperture of aperture array 122. It can be beneficialto align electron beam 20 with the selected aperture (denoted 123).

FIGS. 7 and 8 illustrate first area 121 of aperture array 122 accordingto embodiments of the invention. First area 121 includes apertures 1221,1222, 123 and 1224. FIG. 8 illustrates first area 121 as furtherincluding alignment target 125.

The alignment process can start by scanning with electron beam 20 firstarea 121 of aperture array 122. First area 121 includes multipleapertures of aperture array 122. First area defines a first field ofview of scanning electron microscope. A second field of view of scanningmicroscope can be defined when the object 10 is scanned through aselected aperture 123.

A detector, such as detector 150 or 160, detects particles generated inresponse to an interaction between electron beam 20 and first area 121and sends detection signals to controller 190. Controller 190 mayprocess the detection signals to provide an image of first area 121 andto calculate a spatial relationship (distance, relative angle) betweenselected aperture 123 and a reference location within first area 121.The reference location can be an alignment target 125, a corner of firstarea 121, an aperture that has a unique shape and the like.

Once the spatial distance is calculated controller 190 can control acompletion of the alignment process. The controller 190 can send controlsignals to deflectors, to a mechanical unit that can introduce amechanical movement between interface 120 and scanner 140, and the like.Once the alignment process ends the scanning electron microscope 100 canobtain an image of an area of object 10. The area can include the entireobject 10, a small portion of the object or a large area of object 10.The area of object 10 is scanned by scanning a second area 127 ofaperture array 122. Second area 127 is smaller than first area 121 andcan correspond to selected aperture 123.

The alignment can be done by scanner 140 but can also be done by usingmechanical movements. The alignment can utilize at least one of thefollowing: (i) alignment coils ensuring that the one or more electronbeams are aligned with the one or more apertures; (ii) mechanicalmovement of the aperture array (or at least the one or more relevantapertures); and (iii) mechanical movement of the objective or apermanent magnet relative to the aperture array. The advantage is thatthe moving part is not part of the vacuum sealing.

The mechanical movement of aperture array 122 (or relevant apertures)can be achieved by using a flexible connector between the aperture arrayand another part of the interface. The flexible connector can be movedby a motor (piezo-motor, linear motor and the like).

Either one of the alignment methods mentioned above or combination ofone or more alignment methods can be used also to select one or moreapertures of an aperture array.

In case of mechanical alignment of the aperture, the movement can bemotorized, controlled by a controller and positions can be calibrated orpreset to allow seamless work.

A flexible connector can be also used to connect aperture array 122 toframe 126 of FIG. 1. The flexible connector can control the distancebetween the object and the aperture by moving the aperture array 122 inthe direction perpendicular to the plane of object 10. This has theadvantage of maintaining a fixed distance between the object and theaperture while moving a small mass.

FIG. 9 illustrates method 900 for aligning an electron beam and anaperture of an aperture array, according to an embodiment of theinvention.

Method 900 starts by stage 910 of obtaining an image of a first area ofthe aperture array; wherein the first area includes multiple aperturesof the aperture array. The first area can include the entire aperturearray or a portion thereof. The first are can be selected such as toinclude a selected aperture and at least one other aperture or referencelocation.

Stage 910 is followed by stage 920 of calculating a spatial relationshipbetween a selected aperture of the multiple apertures and a referencelocation within the first area. The reference location can be analignment target or any other unique point within first area.

Stage 920 is followed by stage 930 of aligning an electron beam with thereference location in response to the spatial relationship.

At the end of stages 920-930 an alignment is achieved. Once such analignment is achieved method 900 can proceed to obtaining an image of aregion of an object. Stage 930 can include applying any of the mentionedabove alignment techniques.

Stage 930 is followed by stage 940 of obtaining an image of a region ofan object that is positioned in a non-vacuum environment. Stage 940includes scanning the region by an electron beam that is generated in avacuum environment, passes through the selected aperture and passesthrough an ultra thin membrane that seals the selected aperture. Theultra thin membrane withstands a pressure difference between the vacuumenvironment and the non-vacuum environment.

Stage 940 may includes scanning a second area of the aperture array. Thesecond area is smaller than the first area.

Working Distance

Referring back to FIG. 1, scanning electron microscope 100 can determinethe working distance (defined between object 10 and interface 120 or anypart thereof) by evaluating the relationship between two or threeelements out of: (i) an amount of electrons generated by an interactionbetween an object and the electron beam; (ii) an amount of electronsthat pass through the aperture array; (iii) an amount of electrons thatdo not pass the aperture array but hit the frame that supports theaperture array.

It is noted that these amount can be measured or estimated in variousmanners. For example, the amount of electrons that pass through aperturearray 122 can be estimated by measuring an amount of electrons that aredetected by one or more detectors (such as detector 150) located invacuumed environment 170. Yet for another example, the amount ofelectrons that do not pass through aperture array 122 can be estimatedby measuring an amount of electrons that impinge on aperture array 122or on frame 126 that at least partially surrounds aperture array 122.The overall amount of electrons can be estimated by measuring theintensity of electron beam 20 and by estimating the yield of object10—the yield being the percentage of electrons that are scattered orreflected from object 10. This evaluation can involve illuminating atarget of known characteristics (for example—of known yield) andmeasuring electrons that are emitted from the target, electronsscattered from the target or current that flows through the target.

Each relationship between the mentioned above amounts of electronsreflects the angular distribution of electrons and this angulardistribution is responsive to the working distance. Each workingdistance may be characterized by a unique relationship between thementioned above amounts of electrons.

Controller 190 may determine the distance by at least one of thefollowing manners or combination thereof: (i) in response to acomparison between detection signals generated when the electron beam ispositioned in different locations in relation to the aperture; (ii) inresponse to a comparison between detection signals generated when theelectron beam illuminates the object at different illumination paths;(iii) in response to a comparison between shadows that appear indifferent locations of an image of the area of the object; (iv) byfinding a saturation point; and (v) in response to a size of theaperture and in response to a saturation point; wherein the size of theaperture is set by a shutter.

Another to various embodiments of the invention the working distance canbe determined in response to a change of the collection angle fordifferent parts of the window. FIG. 24 illustrates electron beam 20 thatis positioned at the center of aperture 122 and electron beam 20′ thatis positioned near the right side of aperture 122. Electron beam 20causes particles 445 to impinge on a first detection portion 151 andparticles 444 to impinge on second detector portion 152. Electron beam20′ causes particles 455 to impinge on a first detection portion 151 andparticles 454 to impinge on second detector portion 152.

The available collection angle of particles associated with electronbeam 20 is larger that the available collection angle associated withelectron beam 20′. This difference is larger for longer workingdistances and can be manifested in shading of the image near the edgesof aperture 122. The dependence of the width of the shading as afunction of working distance for a given window geometry can be foundeither by simulation or calibration. For the measurement itself one canuse either discrete points, a line scan crossing the entire window orthe entire image.

FIG. 11 illustrates a portion of scanning electron microscope 100 andvarious particles according to an embodiment of the invention.

FIG. 11 illustrates detector 160 as a current meter that measures thecurrent that flows through frame 126 that is connected to aperture array126. FIG. 11 also illustrates electrons that pass through aperture array122 and are detected by detector 150. FIG. 126 also illustrates acollection angle 1111.

If, for example, the aperture array includes a single circular aperturethat has a radius of r, and the working distance is d then the electronsthat will pass through this aperture are within collection angle 1111(defined in relation to a propagation axis of electron beam 20) thatequals arctangent(r/d). Electrons that are outside this angle will hitframe 126. The collection angle is also referred to as solid angle.

If the working distance is large enough then the relationship betweenelectrons that pass aperture array 122 and those who do not pass it aredependent upon the collection angle and are not substantially affectedby the shape of frame 126. On the other hand, at relatively smallworking distances the shape of frame 126 and especially a slope (if suchexists) of the inner edges of frame 126 may affect the relationshipbetween the amount of electrons that pass through aperture array 122 andthose who does not pass it.

The distribution of particles emitted as a result of an interaction withobject 10 can be known in advance and this distribution can assist, oncethe relationship between the amounts of electrons is measured, todetermine the working distance. For example, back scattered electronsare emitted from object 10 with a Lambert (cos θ) distribution, whereinθ is the angle between the emitted electron and the normal to object 10.The calculation of working distance d can also be responsive to knownlosses.

Table 1 illustrates a relationship between working distances (expressesas multiplication of radius r of a circular aperture), collection angle,percent of electron that pass through the aperture array, percent ofelectron that do not pass through the aperture array, ratio of electronsthat pass aperture array and those who do not pass through the aperturearray, and contrast. The contrast is the ratio between the differenceand the average of two measurements taken at two working distancesseparated by r/2.

In a non-limiting example, if the aperture has a radius of 10 microns,the working distances span is 5 to 100 microns

% % of Ratio of electrons electrons electrons that working that passthat do not pass aperture distance collection through pass array andthose (window angle aperture aperture who do not radius) (radians) arrayarray pass contrast  0.5 1.107 0.894 0.106 8.472  1 0.785 0.707 0.2932.414 1.11  1.5 0.588 0.555 0.445 1.246 0.64  2 0.464 0.447 0.553 0.8090.43  2.5 0.381 0.371 0.629 0.591 0.31  3 0.322 0.316 0.684 0.462 0.24 3.5 0.278 0.275 0.725 0.379 0.20  4 0.245 0.243 0.757 0.320 0.17  4.50.219 0.217 0.783 0.277 0.14  5 0.197 0.196 0.804 0.244 0.13  5.5 0.1800.179 0.821 0.218 0.11  6 0.165 0.164 0.836 0.197 0.10  6.5 0.153 0.1520.848 0.179 0.09  7 0.142 0.141 0.859 0.165 0.08  7.5 0.133 0.132 0.8680.152 0.08  8 0.124 0.124 0.876 0.142 0.07  8.5 0.117 0.117 0.883 0.1320.07  9 0.111 0.110 0.890 0.124 0.06  9.5 0.105 0.105 0.895 0.117 0.0610 0.100 0.100 0.900 0.110 0.06

FIG. 12 illustrates a relationship between the working distance andelectron distribution according to an embodiment of the invention. Curve1210 illustrates the relative amount (fraction) of electrons that do notpass through aperture array 122 while curve 1220 illustrates therelative amount (fraction) of electrons that pass through aperture array122.

FIG. 13 illustrates a ratio between the fraction of electrons that donot pass through aperture array and the fraction of electrons that passthrough aperture array 122, according to an embodiment of the invention.FIG. 13 includes curve 1300 that illustrated this ratio.

FIG. 14 illustrates a contrast; according to an embodiment of theinvention. FIG. 14 includes curve 1400 that illustrated the contrast.

FIG. 15 illustrates method 1500 for observing an object that ispositioned in a non-vacuum environment, according to an embodiment ofthe invention.

Method 1500 starts by stage 1510 of illuminating an area of an objectwith an electron beam. The electron beam is generated in the vacuumenvironment and passes through an aperture of an aperture array andpasses through an ultra thin membrane that seals the aperture. The ultrathin membrane withstands a pressure difference between the vacuumenvironment and the non-vacuum environment.

Stage 1510 is followed by stage 1520 of detecting particles generated inresponse to an interaction between the electron beam and the object.

Stage 1520 can include at least one of the following stages or acombination thereof: (i) detecting electrons generated in response tothe interaction between the at least one electron beam and the object;(ii) detecting photons generated in response to the interaction betweenthe at least one electron beam and the object; (iii) detecting X-rayemission generated in response to the interaction between the at leastone electron beam and the object; (iv) detecting particles by a detectorpositioned within the vacuum environment; (v) detecting particles by adetector positioned within the non-vacuum environment; (vi) detectingelectron current generated as a result of the interaction; and (vii)detecting Cathodoluminescence of the object, fluorescence markers orlight emitted due to electron excitation of gas molecules.

Stage 1520 is followed by stage 1530 of determining a distance betweenthe object and the ultra thin membrane in response to detectedparticles. It is noted that the distance can be determined by anapproach curve generated by several measurements at different workingdistances or by detection signals obtained while the distance betweenthe scanning electron microscope and the object remains the same.

Stage 1530 is followed by stage 1540 of responding to the determinationof the working distance. Stage 1540 can include adjusting a focus of thescanning electron microscope to comply with the working distance,changing the working distance in order to achieve a desired workingdistance, or perform another iteration of stages 1510-1530. Theadditional iteration can be performed in order to increase thereliability of the determination of the working distance.

Stage 1540 can include changing the working distance and jumping tostage 1510. Thus additional iteration of the measurement process can beperformed. This can assist in finding a saturation point or indetermining the working distance-especially if only a single detectordetects particles during stage 1520.

Accordingly, stage 1540 can include altering the working distance andjumping to stage 1510 until a relationship between particles that passthrough the aperture array and particles that not pass through theaperture array maintains constant despite the altering of the distance.This is illustrated by stage 1541 of checking if a saturation point hasbeen detected.

The additional iteration can be executed after changing the workingdistance but this is not necessarily so. The additional iteration canassist in determining the working distance

Stage 1510 can include stage 1511 of illuminating an area of the objectby directing the electron beam to pass through the aperture at a pointthat differs, from a center of the aperture. In this case stage 1520 caninclude stage 1521 of detecting particles by detectors that havedifferent collection regions and stage 1530 can include stage 1531 ofdetermining the distance in response to a relationship between detectionsignals generated by the detectors.

Stage 1530 can include stage 1532 of determining the distance inresponse to a difference between detection signals generated by thedetectors.

Stage 1520 can include stage 1523 of detecting particles by at least onedetector located in the non-vacuum environment and by at least onedetector located in the vacuum environment and stage 1530 can includestage 1533 of determining the distance in response to a relationshipbetween detection signals generated by the detectors.

Stage 1510 can include stage 1514 of illuminating the area of the objectwith an electron beam of a first intensity and imaging a region of theobject by scanning the region with an electron beam of a secondintensity; wherein the second intensity is lower than the firstintensity.

Stage 1530 can include stage 1535 of determining the distance inresponse to a ratio between at least two out of: (i) amount of particlesthat passes through the aperture array as a result of the interaction;(ii) amount of particles that did not pass through the aperture array;and (iii) amount of particles generated as result of the interaction.

Stage 1520 can include stage 1526 of measuring a current that flowsthrough at least one detector.

Method 1500 may include at least one of the following stages or acombination thereof: (i) comprising determining the distance in responseto a comparison between detection signals generated when the electronbeam is positioned in different locations in relation to the aperture;(ii) determining the distance in response to a comparison betweendetection signals generated when the electron beam illuminates theobject at different illumination paths (different angles of incidence,different location in relation to the aperture); (iii) determining thedistance in response to a comparison between shadows appearing indifferent locations of an image of the area of the object; (iv) findinga saturation point; (v) setting a size of the aperture by a shutter andfinding a saturation point.

FIG. 16 illustrates an effect of placing a shutter on the collectionefficiency according to an embodiment of the invention.

In general, the shutter defines the effective size (and even shape) ofan aperture. An aperture of different effective sizes is characterizedby different saturation points as illustrated by FIG. 16. According toan embodiment of the invention the working distance can be determined byfinding the saturation point. The working distance that corresponds to asaturation point can be set by changing the effective size of theaperture—for example, by closing or opening the shutter.

It is assumed that a detector is placed at a distance of 4 mm above acircular aperture, the shutter is located 2 mm above the aperture andthe diameter of the aperture is 250 μm. The collection efficiencydependence on the shutter opening was calculated for three differentworking distances—0 μm (graph 1610), 200 μm (graph 1620) and 400 μm(graph 1630). It is noted that for different working distances, thesaturation point occurs at different shutter diameters.

FIG. 17 illustrates a relationship between working distances and acalculated shutter diameter for onset of signal saturation (equilibriumpoint) according to an embodiment of the invention. The relationship isillustrated by curve 1710.

FIG. 18 illustrates a detector 1800 that includes two concentric annulardetector elements (electrodes) 1810 and 1820 according to an embodimentof the invention. The inner annular electrode 1810 surrounds aperture1830.

FIG. 19 illustrates collection efficiencies for the detector of FIG. 18,as a function of working distance according to an embodiment of theinvention.

Detector 1800 is located 4 mm above an aperture of diameter of 250 μm.Inner annular electrode 1810 has a diameter of 6 mm and surroundsaperture 1830 of diameter of 1 mm, and outer annular electrode 1820 hasa diameter of 9 mm.

Curve 1910 illustrates detection signals (denoted A) generated by innerannular electrode 1810.

Curve 1920 illustrates detection signals (denoted B) generated by outerannular electrode 1820.

Curve 1930 illustrates the difference (denoted A-B) between detectionsignals generated by inner annular electrode 1810 and outer annularelectrode 1820.

FIG. 20 illustrates an illumination of electron beam 20 at a locationthat differs from the center of aperture 123 according to an embodimentof the invention. Aperture 123 is supported by frame 126 and has twoaxes of symmetry denoted 3 and 4. This illumination is also referred toas off axis illumination.

FIG. 21 illustrates an annular BSE detector 2100 having two segments2101 and 2102 according to an embodiment of the invention. BSE detector2100 can be either one of detectors 150 and 160.

FIG. 22 illustrates an off-axis illumination according to an embodimentof the invention.

Electron beam 20 is directed to a location that differs from the middleof aperture 122. Particles such as electrons interact with object 10 andare detected by different portions (different detector elements,different electrodes) 6 and 150. Particles that are directed towardsportion 6 are denoted 444 and particles that are directed towardsportion 150 are denoted 445.

FIG. 23 illustrates a relationship between a difference signal andworking distance for off axis illumination according to an embodiment ofthe invention. Curve 2310 illustrates this relationship. The differencesignal grows rapidly till it reaches a maximal value at a workingdistance of about 150 microns. At distances above 150 microns thedifference signal gradually decreases. It is noted that the workingdistance associated with the maximum may depend only on geometry and isnot sensitive to the sample yield or to the intensity of electron beam20.

The aperture was 250 μm wide and electron beam 20 was positioned 100microns from the center of the aperture. The difference signal isnormalized by its maximal value.

A computer program product can be provided. It includes a computerreadable medium that stores instructions for executing any of thementioned above methods or a combination thereof.

However, other modifications, variations and alternatives are alsopossible. The specifications and drawings are, accordingly, to beregarded in an illustrative rather than in a restrictive sense.

The present invention can be practiced by employing conventional tools,methodology and components. Accordingly, the details of such tools,component and methodology are not set forth herein in detail. In theprevious descriptions, numerous specific details are set forth, in orderto provide a thorough understanding of the present invention. However,it should be recognized that the present invention might be practicedwithout resorting to the details specifically set forth.

Only exemplary embodiments of the present invention and but a fewexamples of its versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein.

1. A method for observing an object that is positioned in a non-vacuumenvironment, the method comprising: generating an electron beam in avacuum environment of an electron microscope; scanning a region of theobject with the electron beam, the scanning comprising allowing theelectron beam to pass through an aperture of an aperture array, passthrough an ultra thin membrane that seals the aperture, and pass throughan object holder; the ultra thin membrane withstanding a pressuredifference between the vacuum environment and the non-vacuumenvironment; detecting particles generated in response to an interactionbetween the electron beam and the object; and imaging the object byanother microscope located outside of said vacuum environment and belowthe object. 2-9. (canceled)
 10. A scanning electron microscope systemcomprising: an electron microscope comprising: an electron beam sourcepositioned in a vacuum environment, the electron beam source beingadapted to generate an electron beam; an interface between the vacuumenvironment and a non-vacuum environment in which an object ispositioned, the interface comprising an aperture array sealed by anultra thin membrane that is substantially transparent to the electronbeam and withstands a pressure difference between the vacuum environmentand the non-vacuum environment; an object holder; a scanner that scans aregion of the object with the electron beam, wherein the electron beampasses through an aperture of the aperture array and passes through theultra thin membrane; and a detector that detects particles generated inresponse to an interaction between the electron beam and the object; andanother microscope located outside of said vacuum environment and belowthe object. 11-61. (canceled)
 62. The method according to claim 1 andwherein said another microscope is an optical microscope.
 63. The methodaccording to claim 1 and wherein said object is imaged by said electronbeam and by said another microscope at least partially simultaneously.64. The scanning electron microscope system according to claim 10 andwherein said another microscope is an optical microscope.
 65. Thescanning electron microscope system according to claim 10 and whereinsaid object is imaged by said electron beam and by said anothermicroscope at least partially simultaneously.